Tap changers for uninterrupted switching between winding taps of a tapped transformer have been known from the prior art for many years. The according tapped transformers to be regulated comprise a stepped regulating winding on the primary or also on the secondary side. The winding on the transformer side to be regulated consists altogether of one fixed part, which is the main winding, and the actual regulating winding that possesses a plurality of winding taps. This is explained in detail, for instance in the publication from the year 2000, “Axel Kramer: On-Load Tap-Changers for Power Transformers”.
It is thus an established state of the art that the tapped transformer to be regulated comprises, on the transformer side to be regulated, a main winding and a stepped regulating winding connected in series thereto.
While earlier tap devices comprised mechanical switching components for switching between the individual winding taps of the regulating winding, vacuum switching components have been in place for a number of years now. More recently, semiconductor switching components for uninterrupted switching between such winding taps have also been proposed. Such semiconductor switching components possess numerous advantages, switching is possible without mechanical components; however they are relatively sensitive to overvoltages. In the prior art, such semiconductor switching components are invariably subject to high stress under lightning voltage exposure when testing the transformer and in the instance of transients in the network (e.g. when switching SF6-/vacuum power switches).